1. Field of the Invention
The present invention relates to a method for forming a conductive layer and a substrate having the conductive layer. Further, the present invention also relates to a method for manufacturing a semiconductor device having a conductive layer.
2. Description of the Related Art
Conventional methods for forming a conductive layer serving as an antenna, a pixel electrode, a wiring, or the like over a flexible substrate include the following: a method in which a composition that contains particles including a metal element is printed over a flexible substrate by a screen printing method and the composition is then heated and baked to form a conductive layer; and a method in which a conductive layer is formed over a flexible substrate by a plating method.
Patent Document 1: Japanese Published Patent Application No. 2004-310502
In order to form a low-resistance conductive layer by using a composition that contains particles including a metal element, the composition is preferably heated and baked at a high temperature, typically, 200° C. or higher. However, depending on a material, some flexible substrates have a low glass transition temperature, which can be lower than a baking temperature of a composition that contains particles including a metal element. Therefore, there is a problem in that a flexible substrate is deformed in a case of directly printing a composition that contains particles including a metal element over the flexible substrate and performing heating and baking to form a low-resistance conductive layer.
On the other hand, in a plating method, a baking step is not necessary, and a low-resistance conductive layer can be formed at a comparatively low temperature from approximately room temperature to 100° C. However, in a plating method, there are problems in that dangerous chemicals such as sulfuric acid, hydrochloric acid, and cyanogens compounds are used and waste fluids cause pollution.
In a case where a composition is printed over a substrate by a screen printing method, compositions which are applied by filling mesh openings of a screen with the compositions are connected with each other so that they become a linear compound. Therefore, a thickness of a region where compositions have been applied by filling mesh openings of a screen with the compositions is different from that of a region where compositions are connected, and further, a composition having a side surface with a curved (uneven) shape is formed.
Accordingly, in a case where a plurality of conductive layers is formed, there is variation in the thickness and shape of conductive layers, and as a result, there is a problem in that variation in resistance of the conductive layers occurs.
When an antenna, such as a wireless chip capable of transmitting and receiving data wirelessly (also referred to as an ID tag, an IC tag, an IC chip, an RF (radio frequency) tag, a wireless tag, an electronic tag, or an RFID (radio frequency identification device)), is formed using such a conductive layer, inductance varies in a plurality of antennas, and a problem occurs in that variation in resonance frequency and electromotive force accompanying it occurs from one wireless chip to another wireless chip.